Non-contacting limit switch

ABSTRACT

A contact-less limit switch for path-responsive release of switching procedures, which comprises a housing, a magnet producing a magnetic field and disposed in the housing. At least one field plate has electric current flowing therethrough, and is disposed within the range of the magnetic field. The resistance of the at least one field plate is variable by the magnetic field, and a member is provided which is operable from the outside for varying within selected limits the density or position of the magnetic field with respect to the field plate.

United States Patent 1151 3,657,685 Pfeffer 1451 Apr. 18, 1972 541NON-CONTACTING LIMIT SWITCH [56] References Cited [72] Inventor: JosefPfefl'er, Amtzell near Wangen, Ger- UNITED STATES PATENTS many 3,509,4664/1970 Lemen ..325/397 [73] Assignee: Raii Raimund Flnsterholze Elekb th h If 'k 21 23 e Ravensburg 3,537,046 10/1970 l-lubrich m1 ..323/94 11x [22] F iled: Jan. 3, 1969 Primary Examiner-Rodney D. Bennett, Jr.

Assistant ExaminerR. Kinberg [21] PP 7889710 Attorney-Ernest G. Montague30 Foreign Application Priority Data [571 ABSTRACT A contact-less limitswitch for path-responsive release of Feb. 10, 1968 Germany ..P 16 38108.1 Switching procedures, which comprises a housing, a magnetproducing a magnetic field and disposed in the housing. At {52] US. Cl..338/32 R, 323/94 H least one field plate has electric current flowingtherethrough [51] Int. Cl. ..I-I0lv 5/00 is disposed within the range fthe magnetic fi ld The Field Search 323/94 1 sistance of the at leastone field plate is variable by the magnetic field, and a member isprovided which is operable from the outside for varying within selectedlimits the density or position of the magnetic field with respect to thefield plate.

6 Claims, 6 Drawing Figures iii", iiil Patented April 18, 1972 I I l I21 I Fig.4

Fig.6-

Inventor.-

NON-CONTACTING LIMIT SWITCH The present invention relates to acontact-less limit switch, in general, and to such a limit switch for apath-responsive release of switching purposes, in particular, wherebyfor production of electronic control pulses one or a plurality ofcurrent-fed field plates, as well as one or a plurality of magnets,relatively movable towards each other, are arranged.

It is known that such contact-less switches, compared with such switcheshaving mechanical contacts, have particularly advantageouscharacteristics, essentially chatter-free contact performance, longlife, constant-remaining transfer resistance, indifference againsthumidity and vibration, a high number of switching actuations and lowoperating force.

These characteristics are particularly important in limit switches,whereby still the following additional conditions are set:Reproduceability of the switching point, high switching exactness,switching speed independently from the operation of the switching-pushrod.

It is, therefore, one object of the present invention to provide acontact-less limit switch, which has the characteristics of the knowncontact-less switches and beyond that also which fulfill the lastmentioned conditions.

It is another object of the present invention, to provide a contact-lesslimit switch, wherein the field plate is disposed within the range of amagnet field, the density and/or position to the field plate is variableby an element movable from the outside and by an operation-push rod inselectable limits, respectively.

With this principle it is possible, to fulfill the mentionedrequirements, whereby depending upon the prevailing special structuraland functional conditions, different embodiments of the contact-lesslimit switch according to the present invention are provided.

With these and other objects in view which will become apparent in thefollowing detailed description, the present inven tion, which isdisclosed by example only, will be clearly understood in connection withthe accompanying drawings, in which:

FIG. I is an axial section of 'the contact-less limit switch, designedin accordance with the present invention;

FIG. 2 is an axial section of the contact-less limit switch includingtwo magnets;

FIG. 3 is an axial section of the contact-less limit switch includingtwo magnets, disclosing another embodiment;

FIG. 4 is an axial section of the contact-less limit switch, showinganother embodiment of the present invention;

FIG. 5 is an axial section of still another embodiment of the presentinvention; and

FIG. 6 is a section of yet another embodiment of the present invention.

Referring now to the drawings, in particular to FIG. 1, a contact-lesslimit switch is disclosed in which in a housing I, made preferably ofsynthetic material, a permanent magnet 5 having pole-shoes 6 and a fieldplate 3 are rigidly secured. An operating push rod 2 is equipped with ashort circuit metal sheet 7, which is movable against the effect of aspring 8 in the direction towards the pole-shoes 6.

In the shown resting position of the switch, the field plate 3 is passedby magnetic lines having a predetermined density, whereby a certainresistance value sets itself in the field plate 3. In order to produce aswitching the short circuit metal sheet 7 is moved in the direction tothe pole shoes 6 by means of the push rod 2. By such arrangement themagnet field is displaced in the circuit metal sheet 7, whereby amaximum is obtained upon engagement between the pole shoes 6 and theshort circuit metal sheet 7. In this position the field plate 3 has thelowest resistance.

The resistance variation can be used in known manner by suitableelectronic means, which are disposed in a chamber 4, for the productionof a switching pulse. In this case the switching point can be setreproduceable, so that a high switching exactness is obtained.

Referring again to the drawing, and in particular FIG. 2, anotherembodiment of a contact-less limit switch is disclosed in which anoperating push rod 2, guided displaceably in the housing 1 carries amagnet 10 having pole shoes 11. A priming magnet 12 is rigidly securedin the housing 1 opposite the pole shoes 11, the pole shoes of thepriming magnet 12 being formed as lock-in metal sheets 13, between whichthe field plate 3 is inserted.

Upon moving the operating the push rod 2, magnet 10 is moved in thedirection of the priming magnet 12. The lock-in metal sheets 13 of thelatter collect the magnetic field lines originating from the pole shoes11 and guide the magnetic field lines through the field plate 3, wherebythe resistance of the latter is increased. Since the equally named polesof the magnets 10 and 12 are disposed opposite each other, the returnsetting force is obtained from the field lines, so that a spring issuperfluous.

In this embodiment the electric function can be reversed by polereversal of one of the two magnets. In this case upon approaching eachother, the effective fields of the two magnets compensate each other andthe resistance in the field plate becomes smaller.

The switching exactness can be increased here by the insertion of two ormore magnet systems with field plates in connection with an electroniccomparison socket.

Referring now again to the drawing, and in particularly to FIG. 3, stillanother not engaging and contact-less limit switch is disclosed therein.A priming magnet 15 with pole shoes 16 and a field plate 3 are rigidlysecured in the housing 1. Here also the pole shoes carry lock-in metalsheets 17, which are disposed at the end-sided outer wall of the housing1.

In this embodiment the resistance variation in the field plate 3 isbrought about such, that a magnet 18 passes by outside of the housing 1in direction of the arrow P. By the lock-in metal sheets 17, themagnetic field increases its density within the range of the field plate3 and thereby increases its resistance. Since no mechanical wear is herepossible, this limit switch has a practically unlimited life term.

If in one of the magnets 15 and 18, respectively, the exciting isreversed, a reverse electric efiect is obtained, as described inconnection with FIG. 2. In this case the magnet 18 is moved in directionof the arrow P, during switching.

In the present embodiment, also a short circuit metal sheet could beused instead of the magnet 18, whereby then the function of thearrangement as disclosed in FIG. 1 would be obtained.

Referring now again to the drawing, and in particular to FIG. 4, acontact-less limit switch operating as a quick break switch isdisclosed. A magnet 20 having a pole shoe 21 is thereby rigidly securedin the housing 1. A field plate carrier 22 with a field plate 3 isdisposed opposite the pole shoe 2] and in addition an abutment 23 for ananchor formed as a seesaw 24 is provided. The latter is mounted on anedge 25 of the pole shoe 21 and has an abutment 26.

The push rod 2 operating the see-saw 24 is guided in a guide bushing 27and is effective by means of an after slide spring 28 on the pressurepin 29, which supports itself on a shorter arm constituting a controllever on the see-saw 24.

In the shown position, the see-saw 24 is secured by the magnet 20 on theabutment 23. If now for release of a switch pulse the operating pushingrod 2 is moved in the direction towards the see-saw 24, at first thespring 28 is tensioned in particular as long until the spring forceovercomes the securing force of the magnet 20, whereupon the see-sawwrenches or tears itself off the abutment 23 momentarily and changes itsposition relative to the field plate.

Since the see-saw 24 has a flow from the magnetic field, by its movementa sudden resistance variation is created in the field plate 3, which canbe used very advantageously for controlling of electronic circuits.

A particular advantage of this embodiment resides in the fact, that incase of creeping operation of the push rod, a safe switching performanceis assured, since the switching point is exactly kept. Furthermore, bycorresponding measurings any selected transmission ratios between themovement of the push rod and of the see-saw can be obtained.

In the chamber 4 the electronic means 30 having a guide plate 31 orearranged, which means are connected directly to the field plate.

Referring now again to the drawing, and in particular to FIG. 5, acontact-less limit switch is disclosed in which a magnet 32 having poleshoes 33 connected with the push rod 2 is displaceably guided in thehousing 1, and is retained in resting position by the spring 34. Thepole shoes 33 are joined towards each other except a small air split 35,whereby at this point a high concentration of the magnetic flux isbrought about.

Upon operation of the push rod 2 and upon movement of the magnet 32against the field plate 3, respectively, the latter is dispensed in theair split 35, whereby the resistance in the field plate varies. By thehigh magnetic field density in the air split 35, the resistancedifference obtainable in the field plate is likewise great, which has afavorable influence on the release of the switch pulse and the switchingexactness.

Referring still again to the drawing, and in particular to FIG. 6, acontact-less limit switch is disclosed, the switching point of which isadjustable. For this purpose one or a plurality of magnets 37, 38 aredisposed on a rotary disc 39, which is mounted in the housing 1, and isadjustable from the outside. The pole shoes of the magnets 37, 38 areequipped again with an air split 40. The field plate 3 sits on a shaft41 concentrically arranged to the rotary disc 39, which shaft 41 can berotated for instance by a toothed segment 42 via the angular lever 43and a pressure pin 44 by means of the push rod 2, whereby the switchingmovement of the push rod 2 takes place against the effect of a returnsetting spring 45, which tensions during the return stroke into theshown resting position, a further return spring 46. The latter can beused simultaneously as connecting conduct between the field plate andthe electronic means.

During insertion of the push rod 2, the angular lever 43 follows themovement of the push rod 2, since it is moved by the pretensioned spring46, over the parts 41 and 42. The field plate is thereby suspended inthe air strip 40 of the magnet 38 and varies its resistance value,whereby the switching is released. The switch timing point can be set byrotation of the disc 39, which feature can be of advantage in a limitswitch.

The design of the switch in accordance with FIG. 6 makes possible theuse as a limit value indicator between plusand minus-tolerances, wherebythen depending upon the deflection of the key, the field plate issuspended in one magnet 37 or the other magnet 38 and produces pulses,which are usable,

for instance, for sorting out during the surface examination of the workpieces.

While I have disclosed several embodiments of the present invention, itis to be understood that these embodiments are given by example only andnot in a limiting sense.

I claim:

1. A contact-less limit switch for path-responsive release of switchingprocedures, comprising a housing,

a movable permanent magnet producing a magnetic field and disposed insaid housing,

at least one field plate having electric current flowing therethrough,

said field plate being disposed within the range of said magnetic field,

the resistance of said at least one field plate being variable by saidmagneticv field,

a member operable from the outside for varying within selected limitsthe density or position of said magnetic field with respect to saidfield plate and fixed position permanent magnet pole shoes disposed insaid housing and carrying a narrow air gap,

a fixed position permanent magnet disposed in said fixed positionpermanent magnet pole shoes,

said fixed plate disposed in said air gap, and

movable pole shoes carried on the ends of said movable permanent magnet,and which project in a direction toward said fixed position permanentmagnet pole shoes of said fixed position magnet, and are dimensionedsuch that with a shifting of said movable permanent magnet in thedirection of said field plate, front surfaces of said movable pole shoescontact corresponding counter surfaces of said fixed position permanentmagnet pole shoes, constituting abutment surfaces operatively limitingthe movement of said movable permanent magnet.

2. The contact-less limit switch, as set forth in claim 1,

wherein said front surfaces of said movable pole-shoes of said movableperrnanentmagnet are parallel to the part of an opposite front surfaceof said fixed position permanent magnet pole-shoes of said fixedposition permanent magnet.

3. The contact-less limit switch, as set forth in claim 1,

wherein both of said permanent magnets arranged inside of said housingare magnetized with equal poles cross to the direction of theirdisplacement relative to each other.

4. A contact-less limit switch for path-responsive release of switchingprocedures, comprising a housing,

a magnet producing a magnetic field and disposed in said housing,

at least one field plate having electric current flowing therethrough,

said field plate being disposed within the range of said magnetic field,

the resistance of said at least one field plate being variable by saidmagnetic field,

a member operable from the outside for varying within selected limitsthe density or position of said magnetic field with respect to saidfield plate,

said magnet has a pole-shoe,

said field plate is rigidly inserted in said pole-shoe, and

a short-circuit metal sheet is spring-biased and movable in thedirection towards said pole-shoe and varying the density of saidmagnetic field.

5. A contact-less limit switch for path-responsive release of switchingprocedures, comprising a housing,

a magnet producing a magnetic field and disposed in said housing,

at least one field plate having electric current flowing therethrough,

said field plate being disposed within the range of said magnetic field,

the resistance of said at least one by said magnetic field,

a member operable from the outside for varying within selected limitsthe density or position of said magnetic field with respect to saidfield plate,

said member operable from the outside comprises a push rod,

a spring operatively connected to said push rod, 1

said magnet has pole-shoes and is displaceably guided by said push rodagainst the force of said spring, and

said pole-shoes lead towards each other defining therebetween a smallair split, into which said field plate penetrates upon operation of saidpush rod.

6. A contact-less limit switch for path responsive release of switchingprocedures, comprising a housing,

a magnet producing a magnetic field and disposed in said housing,

at least one field plate having electric current flowing therethrough,

said field plate being disposed within the range of said magnetic field,

the resistance of said at least one field plate being variable by saidmagnetic field,

field plate being variable a member operable from the outside forvarying within said field plate is disposed on an axis concentric tosaid roselected limits the density or position of said magnetic tary did can t te said air split by the movement field with respect to Saidfield Plate, of said push rod for release of a switching pulse, and

said gnember operable from the outside comprises a push speed reducingmeans are provided f transmission f the a rotary disc settable from theoutside, switch movement of said push rod to said field plate.

said magnet having an air split is secured to said rotary disc,

1. A contact-less limit switch for path-responsive release of switchingprocedures, comprising a housing, a movable permanent magnet producing amagnetic field and disposed in said housing, at least one field platehaving electric current flowing therethrough, said field plate beingdisposed within the range of said magnetic field, the resistance of saidat least one field plate being variable by said magnetic field, a memberoperable from the outside for varying within selected limits the densityor position of said magnetic field with respect to said field plate andfixed position permanent magnet pole shoes disposed in said housing andcarrying a narrow air gap, a fixed position permanent magnet disposed insaid fixed position permanent magnet pole shoes, said fixed platedisposed in said air gap, and movable pole shoes carried on the ends ofsaid movable permanent magnet, and which project in a direction towardsaid fixed position permanent magnet pole shoes of said fixed positionmagnet, and are dimensioned such that with a shifting of said movablepermanent magnet in the direction of said field plate, front surfaces ofsaid movable pole shoes contact corresponding counter surfaces of saidfixed position permanent magnet pole shoes, constituting abutmentsurfaces operatively limiting the movement of said movable permanentmagnet.
 2. The contact-less limit switch, as set forth in claim 1,wherein said front surfaces of said movable pole-shoes of said movablepermanent magnet are parallel to the part of an opposite front surfaceof said fixed position permanent magnet pole-shoes of said fixedposition permanent magnet.
 3. The contact-less limit switch, as setforth in claim 1, wherein both of said permanent magnets arranged insideof said housing are magnetized with equal poles cross to the directionof their displacement relative to each other.
 4. A contact-less limitswitch for path-responsive release of switching procedures, comprising ahousing, a magnet producing a magnetic field and disposed in saidhousing, at least one field plate having electric current flowingtherethrough, said field plate being disposed within the range of saidmagnetic field, the resistance of said at least one field plate beingvariable by said magnetic field, a member operable from the outside forvarying within selected limits the density or position of said magneticfield with respect to said field plate, said magnet has a pole-shoe,said field plate is rigidly inserted in said pole-shoe, and ashort-circuit metal sheet is spring-biased and movable in the directiontowards said pole-shoe and varying the density of said magnetic field.5. A contact-less limit switch for path-responsive release of switchingprocedures, comprising a housing, a magnet producing a magnetic fieldand disposed in said housing, at least one field plate having electriccurrent flowing therethrough, said field plate being disposed within therange of said magnetic field, the resistance of said at least one fieldplate being variable by said magnetic field, a member operable from theoutside for varying within selected limits the density or position ofsaid magnetic field with respect to said field plate, said memberoperable from the outside comprises a push rod, a spring operativelyconnected to said push rod, said magnet has pole-shoes and isdisplaceably guided by said push rod against the force of said sPring,and said pole-shoes lead towards each other defining therebetween asmall air split, into which said field plate penetrates upon operationof said push rod.
 6. A contact-less limit switch for path responsiverelease of switching procedures, comprising a housing, a magnetproducing a magnetic field and disposed in said housing, at least onefield plate having electric current flowing therethrough, said fieldplate being disposed within the range of said magnetic field, theresistance of said at least one field plate being variable by saidmagnetic field, a member operable from the outside for varying withinselected limits the density or position of said magnetic field withrespect to said field plate, said member operable from the outsidecomprises a push rod, a rotary disc settable from the outside, saidmagnet having an air split is secured to said rotary disc, said fieldplate is disposed on an axis concentric to said rotary disc and canpenetrate said air split by the movement of said push rod for release ofa switching pulse, and speed reducing means are provided fortransmission of the switch movement of said push rod to said fieldplate.